My home has a sandstone basement dated from 1870. The previous owner had the basement painted, most probably with one of those white paints used to paint room walls and so. I wonder if there is a solution to take off the paint and let the sandstone surface free. The basement has around 20 sqm and I am trying to avoid the need to scrub the paint off. Will a pressure washing do the job?

The second question is: after cleaning the paint from the sandstone, which colourless product should I use to protect it while letting the stone 'breath'?

A pressure washer might do the trick, but most likely a blast medium ( like walnut shells to prevent damage to the wall)i s in order.....this is a VERY messy solution BTW.
The previous owner might have treated the wall with a primer sealant to keep moisture out, if this is the situation-you might wan to keep the with wash up!